1. Field of the Invention
The present invention relates to a process for producing a novel resin by heating to copolymerize a five-member cyclic compound having a conjugated double bond and/or a Diels-Alder addition product thereof, with a co-dimer of said five-member cyclic compound and 1,3-butadiene, a process for producing a novel hydrogenated resin further including the step of hydrogenating said novel resin and a resin composition containing said hydrogenated resin.
2. Prior Art
It has been already known, for example, from U.S. Pat. No. 3,084,147 that a resin soluble in an organic solvent may be produced from a five-member cyclic compound having a conjugated double bond and/or a Diels-Alder addition product thereof by heating highly pure dicyclopentadiene at a temperature of from 260.degree. C. to 290.degree. C. However, the resin produced by this known process is thermally unstable. Besides, a resin having a higher softening point produced thereby tends to be excessively colored and to be deteriorated in solubility in an aliphatic hydrocarbon solvent.
On the other hand, efforts have been made to produce resins by the copolymerization of cyclopentadiene or dicyclopentadiene with diolefins, and as an example of the fruits of such efforts, British Patent No. 1,356,309 discloses a method of producing a resin by the copolymerization of monomer or dimer of cyclopentadiene with 1,3-butadiene. However, the resin produced by this method is liquid and a resin having a high softening point cannot be produced by this prior art method.
In the meanwhile, there is an increasing demand for a resin composition which may be used as a hot-melt composition, a hot-melt traffic paint composition, a hot-melt tackifier composition and a pressure-sensitive tackifier composition. As the tackifying resinous component or the bonding resinous component, natural resins such as rosin and terpene type resins have been widely used. However, these natural resins are unstable in cost and supply and recently replaced by hydrocarbon resins of petroleum type. However, the prior art hydrocarbon resins of petroleum type have disadvantages in that they are poor in tackifying or bonding property and also unsatisfactory in weather-proof and heat resistant properties with attendant disadvantage of inferior hue.
In order to improve the hue and the heat resistant property of the hydrocarbon resins of petroleum type used in hot-melt compositions, attempts have been made to use aromatic petroleum resins or completely hydrogenated cyclopentadiene type resins. However, these resins are extremely poor in tackifying property, thus leading to reduction in peeling strength.
Although a maleic acid resin modified with rosin is used in a hot-melt traffic paint composition, it is inferior in whiteness and apt to suffer cracking. Therefore, hydrocarbon resins of petroleum type produced from the by-product cracked oil fractions obtained by the thermal cracking of petroleum or the like have been increasingly used up to date in consideration of the merits of cheaper cost and stable supply. However, when an aliphatic hydrocarbon resin produced from a cracked oil fraction containing unsaturated aliphatic hydrocarbons having boiling points ranging within 20.degree. C. to 100.degree. C. is used in a hot-melt traffic paint composition, disadvantages are revealed such that the fluidity becomes worse, that fillers tend to precipitate and that occurence of cracking becomes appreciable. Altneratively, an aromatic hydrocarbon resin produced from a cracked oil fraction containing unsaturated aromatic hydrocarbons having boiling points ranging within 140.degree. C. to 280.degree. C. cannot be also used as the bonding resin in a hot-melt traffic paint composition, since it is poor in weather-proof and heat resistant properties. Also, thermally polymerized resins obtained by heating to polymerize dicyclopentadienes are unsatisfactory in heat resistant and weather-proof properties and bad odor.
In the field of the pressure-sensitive tackifying composition, petroleum resins and coumarone-indene resins have been conventionally used in place of natural resins. However, they have not yet been accepted as those that satisfy the properties required for the component of the pressure-sensitive tackifying composition, since they are poor in mutual solubility with rubbers. In fact, it is pssible to improve the quality of an aromatic hydrocarbon resin to have the properties substantially equivalent to those of the terpene resin by hydrogenating it to convert all or a portion of its aromatic rings to alicyclic rings. However, such hydrogenation need be effected under a severe condition of high temperature and high pressure. Moreover, such hydrogenation is inconvenient from the economical standpoint of view, since a large amount of hydrogen is consumed and the operational cost is increased because of the deterioration of the catalyst caused by the sulfur content originated from the cracked oil fraction.
U.S. Pat. No. 3,084,147 quoted hereinbefore also discloses that a light color resin can be produced from highly pure dicyclopentadiene by heating to polymerize the same at a temperature of from 260.degree. C. to 290.degree. C. However, this resin is unstable and has only an insufficient adhesive property when it is used as the tackifying resin in a pressure-sensitive tackifying composition.
French Patent No. 1,541,090 discloses that a resin for a pressure-sensitive tackifying composition may be produced from a fraction of cracked petroleum having the boiling point of from 20.degree. C. to 280.degree. C. by heating to polymerize the fraction to obtain a resin which is then hydrogenated. However, the thus produced resin is too broad in its molecular weight distribution and unsatisfactory in adhesive property.